Adjustable support for a material handling fork

ABSTRACT

Apparatus for shifting the point of support of a material handling fork so as to balance the fork when handling various loads. A support member, which includes the point of support for the fork, is mounted on a trolley which rides on a guide means. The trolley is moved along the length of the guide means by an elongated coupling, fixed at one end, and moved by a control member having a passage therein forming a bight in the coupling. This movement causes the chain to move the trolley from one end of the guide means to the other. The movement of the control member is preferably brought about by a hydraulic cylinder.

United States Patent [191 Meads et al.

[451 Feb. 4, 1975 4] ADJUSTABLE SUPPORT FOR A MATERIAL HANDLING FORK [75] Inventors: Charles D. Meads, Hellam, Pa.; Paul R. Hefler, Alger, Ohio [73] Assignee: Dico Company, Inc., York, Pa.

[22] Filed: Nov. 12, 1973 [2]] App]. No.: 414,675

[52] US. Cl 294/67 AA, 294/82 A [51] Int. Cl. B66c 1/22 [58] Field of Search 294/63, 67, 67 AA, 82;

[56] References Cited UNITED STATES PATENTS 3,244,446 4/1966 Bopp 294/67 AA 3,275,367 9/1966 Bopp 294/82 A 3,301,420 1/1967 Bopp 294/67 AA FOREIGN PATENTS OR APPLICATIONS 326,271 7/1970 Sweden 294/67 AA Primary Examiner-James B. Marbert Attorney, Agent, or FirmParmelee, Miller, Welsh & Kratz [57] ABSTRACT Apparatus for shifting the point of support of a material handling fork so as to balance the fork when handling various loads. A support member, which includes the point of support for the fork, is mounted on a trolley which rides on a guide means. The trolley is moved along the length of the guide means by an elongated coupling, fixed atone end, and moved by a control member having a passage therein forming a bight in the coupling. This movement causes the chain to move the trolley from one end of the guide means to the other. The movement of the control member is preferably brought about by a hydraulic cylinder.

5 Claims, 7 Drawing Figures PATENTED 9 5 SHEET 10F 3 7% L FI -Ll qHjr. E C

4W3. i LEE lifi C ADJUSTABLE SUPPORT FOR A MATERIAL HANDLING FORK BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to material handling forks, and more specifically to means for shifting the point of support of such forks so as to balance the fork under various loads.

2. Prior Art Suspended material handling forks are often used for moving such items as bricks, concrete blocks, and other construction materials. As opposed to fork-lift type trucks, forks of this type are supported only at a single point, and the position and attitude of the fork depend primarily on the correct balance of the load on the fork. If the center of gravity of the load is too close to the end of the tines, the fork will lean forward with the possible result of dropping the load. If the center of gravity of the load is too close to the frame of the fork, the fork will lean backward and make it difficult to properly stack the load. It has thus been found desirable to be able to move the point of support of such a fork in order to compensate for the change in center of gravity of various loads. U.S. Pat. No. 2,772,794 shows a material handling fork on which the point of support is manually adjustable when the fork is not loaded. U.S. Pat. No. 3,239,072 shows a fork having a point of support which is hydraulically adjustable when the fork is either loaded or unloaded.

The present invention allows for adjustment of the point of support of a fork when it is either loaded or unloaded. It alos allows the point of support to be moved all the way to the forward end of the upper frame member of the fork without extending the upper frame, a feature which allows the fork to be brought closer to vertical objects, and which was not present in any of the prior art devices.

SUMMARY OF THE INVENTION The present invention is an apparatus for shifting the point of support of a material handling fork having a substantially horizontal upper frame, so as to balance the fork from a lift means, such as a cable or hydraulic arm, when handling various loads. A substantially horizontal guide means is attached to the upper frame, and a trolley is so constructed as to be capable of supporting the guide means at any point along the length of the guide means. The trolley comprises a support member which is adapted to be suspended from the lift means, and wheels attached to the support member which are adapted to fit and travel on the guide means. An elongated flexible coupling, such as a captive roller chain, is secured at one end to the movable trolley, and at the other end to the upper frame at a fixed point. A coupling control member is movably mounted on the upper frame and has a passage defining a part of the path of travel of the flexible coupling.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a fork having the apparatus of the present invention, showing the point of support in the rearmost position, and an unbalanced load.

FIG. 2 is a view similar to FIG. 1, showing the point of support in a center position, and a balanced load.

FIG. 3 is a view similar to FIG. 1, showing the point of support in the forwardmost position, and an unbalanced load.

FIG. 4 is a plan view of the upper frame of the fork shown in FIGS. l-3, showing the apparatus of the present invention with the point of support at its rearmost point.

FIG. 5 is a view similar to FIG. 4, showing the point of support at its forwardmost point.

FIG. 6 is a side elevation view of the upper frame of the fork shown in FIGS. L3, showing the trolley at its rearmost point.

FIG. 7 is a view similar to FIG. 6, showing the trolley at its forwardmost point.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus of the present invention can best be understood by reference to the accompanying drawings.

FIGS. 1, 2, and 3 show a typical material handling fork of the type with which the present invention may be used. The fork consists primarily of tines 4, a rear frame 6, and an upper frame 8. In a preferred embodiment, the upper frame 8 is no longer than the tines '4, so as to allow the tines 4 to be moved fully up to vertical objects. However, the upper frame 8 will normally be at least as long as half the length of the tines 4, so as to allow the load to be balanced. The fork 2 is suspended from a lifting means 10, such as a hydraulic arm or cable, at a point of support 12. In order to balance the fork 2 under various loads, it is desirable to be able to move the point of support 12 to different locations on the upper frame 8. Such a function is achieved by the apparatus of the present invention, which can be best understood by reference to FIGS. 4-7. The point of support 12 is defined in the present embodiment by a pivot pin passing through a support member 14. This support member 14 is attached to wheels 16, which are adapted to fit and ride on a guide'means, such as rails 18. The wheels 16 are placed under the rails 18, and therefore, support the rails 18 at any point along the upper frame 8. The support member 14 and wheels 16 together form a trolley 20, which can be moved from a rearmost position'on the rails 18, as shown in FIGS. 1, 4, and 6, to a forward position on the rails 18, as shown in FIGS. 3, 5, and 7.

The movement of the trolley 20 along the rails 18 is brought about by the movement of an elongated coupling such as a captive roller chain 22. The movements of the chain 22 are controlled by a control member 24 which has a passage 26 in which the chain 22 travels, which passage forms a bight in the chain 22. One end of the chain 22 is secured to the trolley 20, and the other end is secured to a fixed point 28 on the upper frame 8. The captive chain 22 can travel only through the passage 26, and along the rails 18.

The control member 24 is movable in a line parallel to the rails 18. Movement along this line may be brought about by means such as a hydraulic cylinder 30 extending from one end of the upper frame 8 to a point on the control member 24. Movement of the control member 24 toward the forward end of the upper frame 8 causes a multiplied movement of the captive chain 22 along the rails 18. Since the chain 22 is secured to the trolley 20, the movement of the chain causes a corresponding movement of the trolley 20 along the rails 18.

This movement is twice the movement of the control member 24 and the cylinder 30, such that a movement of the cylinder 30 of, for example, six inches brings about a movement of the trolley 20 of twelve inches.

Since the point of support 12 is moved twice the distance of any movement of the cylinder 30, the movement of the point of support 12 may extend over the entire length of the rails 18 by the use ofa cylinder 30 which is no longer than the rails 18. Therefore, the point of support 12 may be moved to the forwardmost point of the upper frame 8, such that no portion of the upper frame 8 protrudes forward to interfere with vertical objects which may be in the path of the fork 2 when in use.

We Claim:

1. Apparatus for shifting the point of support of a material handling fork having a substantially horizontal upper frame and substantially horizontal tines suspended from the upper frame, so as to balance the fork from a lift means when handling various loads, which apparatus comprises:

a. substantially horizontal guide means attached to the upper frame;

b. a trolley member adapted to be suspended from the lift means, and to fit and travel on the guide means, so that the trolley member is movable along the length of the guide means, and capable of supporting the guide means at any point along said length; and

c. activating means mounted on the upper frame and operatively connected to the trolley for selectively positioning the trolley at any point along the length of the guide means.

2. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the activating means commprises a hydraulic cylinder.

3. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the activating means comprises:

a. a hydraulic cylinder;

b. a flexible coupling connected at one end to the frame and at its other end to the trolley; and

c. rigid control means forming a bight in the coupling and connected to the hydraulic cylinder whereby the stroke of the cylinder multiplies the movement of the coupling and therefore the trolley.

4. Apparatus for shifting the point of support of a material handling fork as defined in claim 3 wherein the flexible coupling is a roller chain.

5. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the upper frame is of a fixed length, which fixed length is less than or equal to the length of the tines, but greater than or equal to half of the length of the tines. 

1. Apparatus for shifting the point of support of a material handling fork having a substantially horizontal upper frame and substantially horizontal tines suspended from the upper frame, so as to balance the fork from a lift means when handling various loads, which apparatus comprises: a. substantially horizontal guide means attached to the upper frame; b. a trolley member adapted to be suspended from the lift means, and to fit and travel on the guide means, so that the trolley member is movable along the length of the guide means, and capable of supporting the guide means at any point along said length; and c. activating means mounted on the upper frame and operatively connected to the trolley for selectively positioning the trolley at any point along the length of the guide means.
 2. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the activating means commprises a hydraulic cylinder.
 3. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the activating means comprises: a. a hydraulic cylinder; b. a flexible coupling connected at one end to the frame and at its other end to the trolley; and c. rigid control means forming a bight in the coupling and connected to the hydraulic cylinder whereby the stroke of the cylinder multiplies the movement of the coupling and therefore the trolley.
 4. Apparatus for shifting the point of support of a material handling fork as defined in claim 3 wherein the flexible coupling is a roller chain.
 5. Apparatus for shifting the point of support of a material handling fork as defined in claim 1 wherein the upper frame is of a fixed length, which fixed length is less than or equal to the length of the tines, but greater than or equal to half of the length of the tines. 